Tube fitting

ABSTRACT

A castable or die forged fitting allowing transverse tube penetration of a vapor generator tube wall while maintaining constant spacing between wall tubes.

Elite Stats tent [1 1 Kuhn [ Feb. 11, 1975 TUBE FITTING [75] Inventor:

[73] Assignee: Babcock & Wilcox Limited, London,

England [22] Filed: Jam. 16, 1974 [2]] Appl. No.: 433,927

Heinz Kuhn, Oberhausen, Germany [52] US. Cl. 122/235 R, 122/6 A [51] int. Cl. F22b 37/10 [58] Field of Search 122/6 A, 235 R, 235 A,

[56] References Cited UNITED STATES PATENTS 3,354,870 ll/l967 Darlinger 122/235 A 7/1969 Huge 122/235 R 12/1970 Evans l22/235 R Primary Examiner-l enneth W. Sprague Attorney, Agent, or Firm.l. M. Maguire [5 7] ABSTRACT A castable or die forged fitting allowing transverse tube penetration of a vapor generator tube wall while maintaining constant spacing between wall tubes.

3 Claims, 11 Drawing Figures FATENTED 1 i975 3.865.083

SHEET 2 OF 2 TUBE FITTING BACKGROUND OF THE INVENTION This invention relates to a fitting arrangement for transverse tube penetration of the closely spaced tube wall of a vapor generator, and means for flow connecting the fitting into the tube wall while maintaining constant spacing between wall tubes.

The closure walls of a steam generator consist of an arrangement of equally spaced parallel fluid flow tubes interconnected by fins to form a gas tight construction. In this type of wall, both the tube diameter and the tube spacing are limited in size. The tubes are limited in diameter due to the problem of flow stability in parallel tubes with a steam water mixture. The fins, on the other hand, are limited in width in order to be adequately cooled. Although it is desirable to use as wide a fin as possible to increase the heating surface, exceeding the allowable width will lead to material fatigue of the fin and flow instability in the tubes.

As the vapor generator is brought up to operating temperature, the water flowing within the tubes absorbs heat by convection which results in a temperature gradient between the hotter fins and the tubes. This temperature gradient causes the fins to elongate, by thermal expansion, more than the tubes, resulting in longitudinal stresses in the tube-fin material. During cooling of the vapor generator, the stresses are again produced, but in the opposite direction. In the case of excessive fin width, the magnitude of stress coupled with the cyclical changes of direction reduces the elasticity of the material and causes it to become brittle, particularly at the fin-tube connection, which in time may fail and break. A failure impairs the tightness of the enclosure and causes a diminished heat transfer from the fin to the tube, resulting in additional failures due to localized overheating. In addition, flow in stability may occur due to unbalanced heat transfer from the fins to the tubes. Thus, in order to avoid stress failures, it is necessary to refrain from exceeding the allowable width of the fins.

In a closely spaced tube wall, transverse tube penetration through the wall generally involves transverse tubes of larger outside diameter than the permissible fin width, or wall tube spacing. In order to accommodate the larger diameter tubes, it is necessary to bend the wall tubes thereby increasing the tube spacing in the vicinity of penetration, resulting in possible failure of the gas tight enclosure.

Tube penetration arrangements in the prior art call for the use of penetrating tubes of smaller diameter than the fin width, however, this does not provide a solution for present day vapor generators where the transverse tube is larger in diameter than the fin width.

It is the object of this invention to provide a fitting to be welded into an opening in the tube wall at the transverse penetration point which requires no more space between the tube than is already provided for by the fins.

SUMMARY OF THE INVENTION The present invention improves the method of transverse tube penetration of a closely spaced tube wall by means of a fitting whch reduces the space requirement for transverse penetration of the wall while providing a gas tight enclosure.

The improvement comprises a one piece fitting manufactured either as acasting from steel suitable for welding or die forged, having the form of a section of the tube-fin wall with at least two fitting wall tube forms or first tubular segments, interconnected by a fin between adjacent pairs of tube forms, and at least one second tubular segment transverse to an adjacent pair of first tubular segments and projecting out of the fitting wall on both sides thereof. Each of the first tubular segments are provided with a fluid flow passageway through the length of the fitting, and are interconnected and spaced by a fin equal to the spacing between the tubes in the vapor generator wall in which the fitting is to be inserted. Upon insertion of the fitting into the vapor generator wall, the wall tubes and the fitting tube forms are thereby aligned with each other and provide an uninterrupted fluid flow passageway in the wall tubes intersected by the fitting.

The second tubular segment extends between and transverse to the first tubular segments and projects outwardly from both sides of the fitting. The second tubular segment is generally of larger diameter than the fin width and is therefore contiguous to the first tubular segments and since the first and second tubular segments share a common wall the fluid flow passageway through the second segment may have a diameter as large as the fin width. Thus, the second tube passageway shares a common boundary wall with the respective passageways of the first tube segments associated therewith. Therefore, the fitting material contiguous to both the first and second tube segments represents the side wall material of both flow passageways at the point of intersection while the remainder of tube wall of both passageways is composed of the respective tube segments of each. The shared side wall between the first and second passageways represents a saving of side wall material on each side, i.e., a double thickness of side wall material of a transverse or wall tube. The fitting thereby enables a transverse tube with an inner diameter as large as the fin width of the tube wall, to communicate across the tube wall without increasing the fin width in the local transverse area, that is, the wall tubes of the enclosure remain straight and equi-spaced.

The tubular ends of the fitting are bevelled preparatory to welding into the tube wall and to the transverse tube connections.

Therefore, another advantage of this invention is that the membrane wall at the area of penetration is gas tight, and the tubes penetrating the wall are solidly connected to the wall so that there is no impairment to flow stability due to restriction or unbalanced heating. When used for roof penetration, e.g. vertical stringer support tube penetrations, the fitting results in a gas tight roof supported by stringer tubes. Reinforcement of the second tubular segments, when used as above, may be provided by shaping the second tubular segments in the form of a truncated cone extending outwardly from the fitting. Further reinforcement can also be obtained by shaping this segment with a fillet rounding in the area of penetration.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic of a once-through type vapor generator having a gas tight membrane wall enclosure.

FIG. 2 is a section along line II-Il in FIG. 3 of a fitting for detail A in FIG. 1.

FIG. 3 is a section along Line III-III in FIG. 2.

FIG. 4 is a side view in the direction of arrow IV in FIG. 2.

FIG. 5 is a section along line V-V in-FIG. 3.

FIG. 6 is a view of the fitting for detail B in FIG. 1 and a section along line VIVI of FIG. 7.

FIG. 7 is a section along line VII-VII of FIG. 6.

FIG. 8 is a view in the direction of arrow VIII in FIG. 9 of a fitting for details C and D of FIG. 1.

FIG. 9 is a plan view of FIG. 8.

FIG. 10 is a section along line XX of FIG. 9.

FIG. 11 is a section along line XIXI of FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a once through type vapor generator with a furnace 1, a horizontal pass 2 and a down pass 3 enclosed by membrane walls 4. The walls are composed of tubes 5 (shown on FIG. 3, FIG. 6, FIG. 8 and FIG. 10) of diameter 10 and fins 6 (FIG. 3) welded 7 together to form a gas tight enclosure. The width 8 of the fins are limited to an allowable maximum value, as explained above. Generally, this allowable width is small which results in a close spacing 9 of the wall tubes.

The enclosure walls are intersected in a plurality of places as indicated by A, B, C and D in FIG. 1, at which the invented fitting can be used to advantage.

At location A, a plurality of stringer support tubes 12 are shown which cross the roof wall 4. The stringer tubes are supported from the vapor generator support steel 13 and serve to carry the tube bundles l4 and 14. The stringer tubes are also used to carry the membrane wall 4 which forms the furnace roof.

A typical fitting for the transverse tube intersection of detail A is shown in FIGS. 2 to 5. The fitting is made of a solid piece by casting or die forging and is shaped to the characteristics of the tubular wall, i.e. a minimum of two coplanar tube forms or first tubular segments l8 separated by a fin 6' of thickness and width 8' respectively equal to the tube wall dimensions. Because the tube forms 18 are welded to the enclosure wall tubes 5, a passageway 18A equal to the inner diameter of the tubes 5 is provided through the tube forms to provide flow continuity through the wall.

The second tubular segment 19 is symmetrically located on either side of the wall and between and contiguous with the first tubular segments 18. The projection 22 of this second tubular segment is provided with a circular edge 20 for welding to the transverse stringer tube 12. A passageway 21 is provided through this second segment concentric with the welding edge 20. This passageway corresponds in size to the inner diameter of the transverse stringer tube 12, and may be as large as the fin width 8 (FIG. 3).

The space requirements at the penetration area of a transverse tube and the vapor generator wall would at least include the diameter of the transverse tube 12. With the fitting, however, it can be seen in FIG. 3 that a saving of twice the thickness of tube material is obtained by the second tubular segment 19 which serves as both the side wall for the fitting wall tubes 18 and the transverse tube 12. In this example, the material thickness ll of the second tubular segment 19 serves this dual purpose.

The material thickness 11 is not overloaded by tension stresses due to internal pressure within the tubes,

since these stresses act in the tangential direction to the passageway and the resulting stress is the vector sum not the algebraic sum of the component stresses. Also, the tube bundle load supported by the stringer tubes does not overly stress the material at the thickness 11 because the segments 19 are conically shaped and are provided with a rounded fillet 23 for further reinforcement at the material cross section 24.

The fitting is welded to the tubes 5 and along the tube-fin border 7', which properly closes the openings in the vapor generator wall. The transverse tube 12 is then welded along the ring edge 20, such that the passageway 21 provides the cross flow conduit through the membrane wall.

FIGS. 6 and 7 show the fitting used according to this invention for the example shown at locationB (FIG. I), where a plurality of tubes from the tube bundle (platens) 14 cross the enclosure wall 4. The fitting of FIGS. 6 and 7 is materially the same as the fitting shown in FIGS. 2 to 5 except that there are provided a plurality of projections 19 (FIG. 7). A typical fitting of this type has two first tubular segment-passageways 18A for the flow in the enclosure wall, and a plurality of second tubular segment-passageways 21, three shown here, for the cross flow penetrating the wall. The center to center distance 25 between passageways corresponds to the spacing of the tubes in the tube bundle 14 (FIG. I).

FIGS. 8 to 11 show the invented fitting for use at enclosure wall locations which cross each other at an arbitrary angle, such as represented by C and D (FIG. 1). The fitting according to FIGS. 8 to 11 is, again, materially the same as the fitting of FIGS. 2 to 5 except this fitting has several first passageways 18A for the flow in the tube wall and the same number of second passageways 21 for the crossing flow. The second tubular segments are equally spaced 9, and are provided with fins 26, with a welding edge 27 and welding edges 20. In this way, the flow in the intersecting enclosure walls cross each other without increasing the fin width even through the tube spacing 9 is narrow.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A vapor generator including spaced fluid heating tubes, some of said tubes being interconnected by webs to form wall means defining a gas enclosure, wherein the improvement comprises at least one fitting of unitary construction seal weldably connected to said wall means and including a plurality of uniformly spaced coplanar first tubular segments, means sealing the spacing between adjacent first tubular segments, each of said first tubular segments being flow connected to a corresponding wall tube, at least one second tubular segment extending through the sealing means in cross flow relation and contiguous to said first tubular segments, said second segment being flow connected to one of said fluid heating tubes.

2. The combination according to claim 1 including a plurality of coplanar second segments wherein each of said second segments extend between different pairs of adjacent first segments.

3. The combination according to claim 1 wherein the end portions of said second segment are in the form of a truncated cone.

* k w a 

1. A vapor generator including spaced fluid heating tubes, some of said tubes being interconnected by webs to form wall means defining a gas enclosure, wherein the improvement comprises at least one fitting of unitary construction seal weldably connected to said wall means and including a plurality of uniformly spaced coplanar first tubular segments, means sealing the spacing between adjacent first tubular segments, each of said first tubular segments being flow connected to a corresponding wall tube, at least one second tubular segment extending through the sealing means in cross flow relation and contiguous to said first tubular segments, said second segment being flow connected to one of said fluid heating tubes.
 2. The combination according to claim 1 including a plurality of coplanar second segments wherein each of said second segments extend between different pairs of adjacent first segments.
 3. The combination according to claim 1 wherein the end portions of said second segment are in the form of a truncated cone. 